1. Field of the Invention
The present invention relates to a solid-state image capturing device, a method of driving a solid-state image capturing device, and an image capturing apparatus, and particularly, to a solid-state image capturing device which is used together with a mechanical shutter, a method of driving the solid-state image capturing device, and an image capturing apparatus having the solid-state image capturing device.
2. Description of the Related Art
A solid-state image capturing device is classified into an X-Y address type solid-state image capturing device represented by a CMOS (Complementary Metal Oxide Semiconductor) image sensor and a charge-transfer type solid-state image capturing device represented by a CCD (Charge Coupled Device) image sensor. Here, in the CMOS image sensor, a random access of a pixel signal is possible. In addition, compared with a CCD image sensor, the CMOS image sensor is capable of rapidly reading the pixel signal while ensuring high sensitivity and low power consumption.
However, in many CMOS image sensors, an electronic shutter function is provided so as to electronically start a new signal charge storage operation by resetting signal charges stored in a photoelectric converter. The shutter type of the electronic shutter function of the CMOS image sensor is a so-called rolling shutter (called a focal plane shutter) type in which an exposure start and an exposure end are set for each pixel row of plural pixels arranged in two dimensions.
Accordingly, in the rolling shutter type CMOS image sensor, the exposure periods for the pixel rows are deviated (different) from each other while in a global shutter type CCD image sensor the exposure of all pixels starts at the same timing. In addition, when the exposure periods of the pixel rows are deviated from each other, a captured image is distorted.
Therefore, in the past, the CMOS image sensor was used together with a mechanical shutter for selectively shielding light incident onto a light receiving surface of the CMOS image sensor so as to have the same exposure period in all pixel rows (For example, see Japanese Unexamined Patent Application Publication No. 2006-191236).
In detail, when the mechanical shutter is opened, and the pixels of all the pixel rows are simultaneously reset, the signal charge storage operation starts. Then, the mechanical shutter is closed so as to end the exposure. After the exposure ends, pixel signals are read for every pixel row. According to a series of operations, since the exposure periods for all the pixel rows are equal to each other without any deviation, the captured image is not distorted.